Process for converting petroleum hydrocarbons



Jamie/747395 w 7 Artemi V- A ma 17, 1928. 2,666.19

W. M. CROSS PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS Filed July 20,.1925

mam-wax EVAPORAZ'DAS Patented Apr. 17, 1928.

PATENT OFFICE.

WALTER 1V1. CROSS, OF KANSAS CITY, MISSOURI.

PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS.

Application filed July 20, 1925. Serial No. 44,781.

This invention relates to improvements in a process for convertlngpetroleum hydrocarbons, and refers more particularly to a.

distillation process in which crude oil and the like is separated into aplurality of fractions of different boiling points, the separation beingmade in anefiicient manner and heat conserved throughout the system byare, to provide a process in which oil is pre liminarily heated inpreheatingcoils positioned-in the top 'of refluxing towers, thencepassed to a preliminary heating stage in which the oil is raised to atemperature sufiicient to vaporize certain of the lower boiling pointfractions; to provide a process in which this preliminarily heated oilis thence passed to a vaporizing stage where a separation is made andthe liquid bottom returned and reheated to temperature suflicient todrive off further fractions of relatively' higher boiling points; toprovide a process in which'overhead material is taken from the separatestages of vaporization and separately subjected to dephlegmation, afterwhich the products are combined, av final distillate recovered andintermediate cuts in the form of liquid condensates removed from theseparate stages of treatment, and further, to provide an apparatus forcarrying out this process.

The single figure is a diagrammatic side elevational view of theapparatus, with'parts in section and parts broken away. I

Referring to the drawing, at 1 is shown a furnace divided by a bafiie 2into a combustion space 3 and a heating chamber 4. The combustionchamber is preferably heated by means of gas burners such as thatdiagram;

matically shown at 5. A heating coil comprising a lower preheatingsection 6 and an upper heating section 7 are positioned in the heatingchamber and are there subjected to the high temperatures of, thecombustion gases passing'from the combustionspace 3 through the heating,chamber and out through the flue pi e 8. 'The tanks 9 and 10 arevaporizing c embers; 11 and 12 are fractionating towers in which the.vapor's from the separate vaporizing towers are treated. 13 is acondenser box in which is positioned a condenser coil 14:; at 15 isshown a receiving tank having a gas relief line 16 controlled by avalve- 17 and a liquid drawoff line 18 regulated by a valve 19.

At 20 is shown a charging pump by means of which crude oil, or any othersuitable type of charging stock, is introduced from storage through theline 21 and is forced through the pipe 22 successively through thepreheating coils 23 and 24 positioned in the towers 12 and 11,respectively. By circulation through these coils, the charging stock 1is preheated by the hot hydrocarbon vapors in the separate towers and ispassed thence through the line 25 to the preheating coil'6 in the lowerpart of the heating chamber of the furnace 1. In this coil 6 heat isadded to the oil to raise it to a temperature at which the lighterfractions will vaporize. The discharge line 6 from the preheating coil,to-

gether with subsequent heating coils designated as 26 and positioned inthe heating chamber between the preheating coil and the final heatingcoil 7, have their outer extremities connected into a header arrangementwhich consists of two vertical pipes '27 and 28 between which areintermediate connecting pipes 29 which constitute extensions.

ate these connecting lines, are valves 28 to 28, inclusive. In thevertical pipe 27 are corresponding valves numbered from 27 to 27,inclusive. The oil, on being preheated in the coil 6, may be dischargeddirectly into the vaporizing chamber 9 through the line 6 by closing thevalves 27 and 28 and opening the valve 29 fer-red directly to thevaporizing chamber 9 from which the volatilized material passes overheadthrough the vapor line 30 and is introduced into the bottom of therefluziing tower 11. This tower is preferably of the bubble tower type,but any suitable type of refluxing tower may be used in its stead. Inthis tower the vapors rise through a series.

of pools, passing off through the line 31 to the final condensing coil14 and thence to the receiver 15. The unvaporized material or bottomchllecting in the chamber 9 is drawn The oil then is trans-' beyond thevalve 29 off through the pipe 32 which is connected With the suctionside of the pump 33. In this Withdrawal line from the chamber 9 may beinterposed an automatic liquid level regulating device and a storagetank not shown which would serve to regulate the withdrawal from thechamber 9 and maintain at all times a head of oil for the pump 33. Thesedetails have purposely been omit ted for simplifying the drawings. Thebottoms from the chamber 9 are discharged by thepump 33 through the line34 which connects into the vertical pipe 28. In the event that the oilis being drawn from the preheating coils in the furnace through thedischarge line 6, the valves in the header arrangement will be soarranged that the oil will travel downwardly through the pipe 28 andinto the lowest intermediate connection 29 through the valve 29 which isopen and into the lowest of the intermediate heating coils 26. It willthen continue upwardly through the remaining coils 26 which areconnected up as a continuous coil by closing the subsequent valves. 29to 29, inclusive, and opening the valves 27 to 27?, inclusive. In a likemanner, if the oil is not given sufficient heat by the lower preheatingcoil 6 by closing the valve 29 it may be circulated on up through theintermediate coils 26 by proper manipulation of the valves in the headerarrangement and discharged from any one of these intermediate heatingpipes through the header arrangement by directing the oil from thetermination of any one of the coils 26 downwardly through the verticalpipe 28 and thence into the evaporating chamber through that portion ofthe line 6 When the oil is circuated in this manner, the bottomsreturned to the pump 33 must be circulated back into the next succeedingcoil 26 above that through which the oil .is discharged when passingthrough the vaporizing chamber 9. Thus, at all times the coils in thefurnace will be maintained full of oil, preventing carbon accumulationand coking and failure of the tubes as a result of dryness. The upperextremity of the vertical line 27 is connected to the coil 7 whichterminates in a transfer line 35 which is connected into the bottom ofthe evaporating chamber 10. Thus, the bottoms returned fromthe chamher 9are given additional heat or are re- .heated to the extent that furtherof the relatively higher boiling point fractions are distilled off ontheir being discharged into the chamber 10. It will be noted that thisupper coil 7 is in a hotter portion of the furnace and therefore the oilcirculating therethrough receives considerably greater heat. The numberof coils which will constitute the three stages of heating in thefurnace, namely the preliminary stage, the

intermediate stage and the upper heating stage, is a lnatter ofengineering and no attempt has been made in the drawings other than adiagrammatic showing of the manner in which the coils are connected up.

The material vaporized in the chamber 10 passes oif through the vaporline 36 and is discharged into the lower part of the tower 12 which isshown as a bubble tower of similar construction to the tower 11. In thistower the-vapors rise through a series of oil pools, being subjected tofractionation in their travel from the bottom of the tower to the topfrom which the still vaporized products pass off through the line 37 andare introduced near the bottom of the tower 11 where they are mixed andpass upwardly with the vaporized material arriving in this tower fromthe vaporizing chamber 9. The combined material passes olf through theline 31 to the condenser 13 and is finally collected in the receivingtank 15. The bottoms from the tower 10, which will consist of theheavier residual material unvaporized in the chamber, is drawn offthrough the line 38 regulated by a valve 39 which may be automaticallycontrolled by a liquid level regulator, not shown, if desired. Thishighly heated material passes thence through a coil 40 positioned in thebottom of the tower 11 and is discharged therefrom through a line 41regulated by a valve 42 to a cooler and thence to storage, or forsubsequentrerunning and cracking or conversion in a separate apparatus.

The refluxed condensate collected inthe bottom of the tower 11 drawn-offthrough the line 43 regulated by a valve 43 which is preferablycontrplled by-a liquid level regulating device (not shown) forthepurpose of maintaining the liquid level in the tower 11 above, inorder to' maintain the coil 40 llO through the coil 44 is finallydischarged through the line 45 controlled by a valve 46 into a cooler,storage tank or utilized as cracking stock. In order to maintain aproper flow of this condensate 'fromthe tower 11 through the tower 12,it may be necessary to lower the tower 12 somewhat in order that aproper gravitational flow will result or a suction pump may be put uponthe discharge line to assure proper circu-- lation. Condensate separatedout in the tower 12 is drawn ofl through the line 47 regulated by avalve 48. This latter valve I from the bottom of the tower 12 throughthe is preferably manipulated by an automatic liquid level regulatlngdevice to maintain a level of oil above the coil 44. J

In actual operation where crude oil is charged to the system, it will bepreheated in the coils 23 and '24 in the tops of the towers 12 and 11and in the coil 6 it will receive additional heat sufficient to vaporizethe lighter fractions therefrom. On discharge to the vaporizing chamber9 these lighter fractions will be taken overhead through the line 30 andsubjected to a refluxing action in the tower 11. The returned bottomsfrom the chamber 9 will be circulated back through the coils 26 and 7 toreceive further heating in order to vaporize additional fractions ofrelatively higher boiling point than those separated off in the chamber9. This hot oil, on being discharged through the line 35 to the chamber10, separates these fractions in the form of vapor which passes offthrough the line 36 to the tower 12 where they are separatelyfractionated from the vapors discharged from the chamber 9 while thebottoms from the chamber 10, which consists primarily ofa fuel oilbottom, passes off through the reboiling coil 40 in the bottom of thetower 11 and thence to storage. It may be necessary to' lower thetower*11 from the' position shown in the'drawing to assuregravitationalflow or to interpose a positive circulating means such as a pumppreferably in the discharge line 41 or beyond a fuel oil cooler (notshown).

Returning now to the material which is uncondensed in the tower '12,these vapors pass off through the line 37 into the bottom of tower 11where they are combined and rise upwardly with the material transferredto the tower from the chamber 9 through the vapor line 30. The combinedfractions are dephlegmated in the tower 11 and the still volatilematerial passes off through the line 31 to be collected as benzene ornaphtha in the receiving tank 15. A condensate having thecharacteristics of gas oil is removed line 47, while a somewhat lightercut, such as a kerosene distillate, is taken off from y the tower 11through the line 43 and utilized as a reboiling agent in the tower. 12.In a process of this character, the distillat1on temperature to whichthe oil is raised in the coils in the furnace may be selected to givethe most complete stripping of the initial-fraction, thus eliminatingsuperheating of these fractions with the formation of unnecessary andobjectionable amounts of mcondensible gas produced where the entire bodyof oil is raised to temperature sufiic ent to distill the higher boilingpoint fractrons. By treating the crude in this manner,

the equilibrium is immediately upset by removing the lighter gases andvapors in I the initial vaporizing stage so that material recovered fromthe remaining oil products such as the gas oil and\kerosene distillateor fuel oil recovered from the subsequent stages, produce a bettercrackmg stock WhlCh gives increased yields and a better final resultingdistillate. Thus, a bigger yield of gasoline is obtained not only fromthe strip ping, but also from thecracking of the remaining petroleumhydrocarbons. The con servation of heat cuts down the fuel becausesuperheating of the oil is eliminated. Furthermore, the elimination ofthe lighter fractions by the use of a vaporizing stage interposedbetween the separateheating stages,

friction loss, due to the accumulation of vapors and gases, is dispensedwith. To overcome this friction loss, a certain amount of pressure mustbe maintained which increases the cost of theapparatus in recoveringdistillate not as good in uality as that recovered in thehereinbeforeescribed proc bers and the bubble towers are heavily insulated to avoidloss of heat through radiation.

I claim: as my invention: 1. A process of distilling petroleumhydrocarbons, comprising the steps of heating the oil in a-prelimin'aryheating stage to a temperature to vaporize the lighter hydrocarbons,passing said heated oil to a, vaporizing stage and there separating theliquid and volatilized material, returning the liquid products forfurther heating to vaporize additional fractions of higher boilingpoints, and passing the reheated material to a separate vaporizmg stageand controlling the relative heating to which-the charging stock andrecycled stock are subjected by limiting through the Heating zone.

2. A process of distilling petroleum hydrocarbons, comprising the stepsof "heating extent of their circulationthe oil in apreliminary heatinstage to a temperature to vaporize the lig ter hydrocarbons, passingsai'd heate d oil to a vaporizing stage and there separating the liquidand volitized material, returning the liquid products for furtherheating to vaporize additional fractions of. higher boiling points,

and passing thereheated material to a sepa- 3. A process of distillingpetroleum hy-- drocarbons, comprising the steps of heating the .oil toa. temperature to vaporize the light hydrocarbons, passin'githe heatedoil to a vaporizing stage,-separatmg the hqmd and vapor, returning theliquid for fur ther heating to vaporize additional fractions of higherboiling point, passing the reheated materials to a separate vaporizing.stage, separately refluxing the volatized fractions and removingdistillates having relatively difierent boiling point ranges, utilizingthe heat contained in the liquid bottoms to redistill low boiling pointproducts in the system ancl'controlling the relative heating 1 of thecharging stock and recycled stock by the extent of circulation of saidstocks through the heating zone.

WALTER M. GROSS.

